A high-performance liquid chromatography method with electrochemical detection (HPLC-EC) was developed for the quantitative determination of the antitumor agent, Spiromustine (SHM) in dimethyl acetamide, intralipid and plasma. The method which has a limit of detection of 30ng SHM/ml and facilitates direct sample injection into the HPLC system was used to determine the stability of spiromustine in 10% dimethyl acetamide and the intralipid vehicle used for the drug's administration. Preliminary data indicate potency losses of 86.7% in ten percent DMA in 18 - 20 minutes and 40.9% in the intralipid vehicle in 62 minutes. Quantitative determination of SHM in plasma and CSF samples from a patient who received a dose of 9.9 mg of the drug is currently in progress.